I was in denial stage until we picked Python 3 for a project at work. Then I went into anger and bargaining with the other dev on the project. Heh. blush
Being forced to come to terms with Python 3 has made me see the light, though. I still have a host of personal projects in Python 2, but anything new I write is in 3.
For me, it was concurrent.futures that pushed me into acceptance stage.